The invention relates to a passenger seat arrangement wherein the two seats are supported side-by-side on a support base which consists of box section frame members on which one of the twin seats is firmly mounted whereas the other is sidewardly movable for adjustment of the spacing between the two seats.
Such box section frame members are utilized particularly in buses where the firmly mounted seat is located adjacent the side (window) wall of the bus and the inner movably supported seat is located adjacent the aisle. Sideward movability of the inner seat permits adjustment of the distance between the window seat and the aisle seat for increased comfort of the passengers during travel at the expense of aisle space. During boarding and unboarding however the seats must be moved together to facilitate passenger traffic through the aisle between the seats.
The structure allowing for side movability of the seats however is relatively expensive and is used therefore only in connection with more luxurious seating. Luxurious seats are generally quite heavy since they are provided not only with better and heavier upholstery than standard seats but they also have, for example, tiltable backrests and leg rests and other devices which provide for increased comfort but which all together substantially increase the weight of such seats. During sudden deceleration, for example, during an accident, the weight that is the mass of these seats must be accommodated by the seat itself and also its support base. It also is to be taken into consideration that, during such sudden deceleration, specifically during and after an accident, the space between the backrests of a seat and the seat ahead becomes the survival space for a passenger. It is therefore necessary to retain passengers, who, during rapid deceleration, are projected forwardly toward the backrest of the seat ahead, in such a manner that energy is consumed in order to avoid injuries as much as possible. Generally, the backrest of the seat ahead is designed to fulfill this need but this requires that the support base is sufficiently strong to retain the seat thereby permitting the backrest to fulfill its energy absorbing design purpose. It also requires that, for sidewardly movable seats, the seat support bearing structure providing for the transverse movability is capable of accommodating the large forces effective during an accident generally in a direction normal to the seat support bearing providing for seat sideward movability.
In present arrangements the box section frame members of the bases of such twin seats are either offset such that the upper side of the transverse bearing structure disposed on the inner offset frame member portion is at the same level as the outer portion of the frame member so that both seats mounted on the support base have the same height, or the box section frame members are straight and spacers are disposed under the firmly mounted seat in order to compensate for the height of the transverse bearing structure. Both arrangements reduce the leg room for the passengers behind and therefore impair the comfort of these passengers.
It has already been pointed out that the transverse bearing structures needed for the lateral movement of the passenger seat are subjected to large forces effective in a direction normal to their longitudinal extent. Since the box section frame members mounted on the support bases can be considered to be a fixed anchorage structure, the transverse bearings need to be designed for the tilting torque which increases exponentially with increasing seat height over the transverse bearing structure. This requires the transverse bearing structure to be very rigid so that they become quite expensive and also quite heavy which increases the dead weight of the structure. In addition the transverse bearings should be rattle-free under any circumstances, whether they are or are not under load. In order to meet all these requirements these transverse bearings have always been of a rigid, heavy and expensive design.
It is the object of the present invention to provide for a seat support arrangement which permits elimination of the heavy and expensive transverse seat support bearings.